Electra with Clipping diodes on emitter.

[gjcamann]

So I've conceived this idea. If you start with a simple tranny booster with a cap on the emitter to boost the highs, Kind of like the AMZ Mosfet Booster http://www.muzique.com/schem/mosfet.htm, but can be done with any tranny really.

Now you put a set of clippers in series with the emitter cap to ground. I dreamed this up last night, will probably get a chance to try it next week.
Anyone try this before or have any suggestions.

[pinkjimiphoton]

yes, i've done it on a couple of my pedals. it's a cool sound. well done.

if memory serves, this is on my toneblaster, maybe the suzy q, too... also did something similar called a "bias clipper".

do a search maybel.... love to hear what ya come up with!!

[midwayfair]

Is this a form of soft clipping? I've been looking for a transistor soft slipping that works at lower gain than feedback loop diodes.

[pinkjimiphoton]

if you use asymetric clipping, yah, kinda... it only conducts when there's signal present, gives it a kinda cool buzzy sound... depends on what diodes, leds. some transistors it doesn't seem to do squat, but predictably ge ones seem to like it.

it's not really soft clipping.... if ya look up my toneblaster, someone posted shots of the way it clipped, it's cool.. it's very asymetrical, and comes on real slow until suddenly it conducts and squares off the wave. makes it wicked volume knob and touch sensitive....

check it out:

[PRR]

Not clipping at all. (Stuff in the emitter leg tends to do the opposite of stuff hung off the collector.)

Small signals see no bypass and get low gain. Signals over 0.5V in see the bypass and get big gain.

"Anti-clipping".

Instead of flattening the peaks, it pushes them way up.

[midwayfair]

Not clipping at all. (Stuff in the emitter leg tends to do the opposite of stuff hung off the collector.)

Small signals see no bypass and get low gain. Signals over 0.5V in see the bypass and get big gain.

"Anti-clipping".

Instead of flattening the peaks, it pushes them way up.

okay, now THAT's intriguing. I can see some interesting gate-type usages, too.

[gjcamann]

Thanks pink jimi, those videos are great, I think that toneblaster has alot of promise.
Here's a little ascii art to show the circuit i'm thinking of.

Code Select Expand


     |
-----|<
     |
     |---------
     |        |
     >       ===
     >        |
     |     <clippers>
     |        |
                 

So this has the emitter resistor, with a cap and clippers in parallel with the emitter resistor. The cap boosts the high freq signals (like in alot of love pedal type designs, or the madbean LaVache www.madbeanpedals.com/projects/LaVache/docs/LaVache.pdf‎), but then they get clipped by the diodes. This branch may need a pot in it.

[pinkjimiphoton]

hey guys,
check out this: http://www.diystompboxes.com/smfforum/index.php?topic=100372.msg884520#msg884520

run the falstad sim, you'll see what i was trying to describe...weird clipping.

if ya read down the page, there's some analysis of what MAY be happening..

but the diode at e does work.... maybe it's what is causing the "anti-distortion" paul speaks of, which is why it acts so dang funky.

it's almost like it tries to stay clean right up til it clips, and then it clips hard... gives a very asymetric clip.

not saying i'm right by any means, but it does something... run the sim!

[midwayfair]

Code Select Expand


     |
-----|<
     |
     |---------
     |        |
     >       ===
     >        |
     |     <clippers>
     |        |
                 


Doesn't work. Basically, the diodes ARE the AC bypass Just replace the whole emitter shebang with back-to-back diodes. Interestingly, the cap to ground will then do nada, and you'll be scratching your head how to get the gain and output back up. There is a way to make the AC bypass cap work though: Reference it to the 9v instead.

I'll post a project in a bit that uses the emitter trick. This was kind of the final piece in a puzzle I've been brainstorming for well over a month. Thanks for pointing this out (and thanks Jimi for the prior art proof that it works).

[pinkjimiphoton]

thanks jon for the info!

yah, i found a pair of diodes worked best.... i forget who, i think maybe it was gus said to just use one, but it doesn't sound the same.